Tag Archives: hackfest

Around a dozen people met inside the Red Hat offices in Brno last weekend. The attendees came from various distributions and projects to discuss and work on color management for Linux. Most people arrived at Thursday and we started immediately to brain storm ideas and share information.

I was quite shocked as I heard Dantii could not join us. Fortunately the last messages about him sound very encouraging. It is great that our community could in different ways help him and his family.

The basic concept we worked with during the hackfest, was the opt-out of colour management approach. That was visible in printing and in window manager colour management.

Printing people discussed the PDF/X OutputIntent. The concept was developed to overcome the current short commings in the cupsICCprofile, which is primarily a vendor solution for CUPS print servers and the colord user session hook inside CUPS server. The implementation of the concept was done inside libCmpx, which is basically a wrapper around Ghostscript, which does the majority of the work, and a interface to Oyranos. From the other side John Layt looked into that work and Krita new print colour management tab to understand the implications for the KDE/Qt print dialog. He discussed lively with Till Kamppeter, Richard Hughes, Chris Murphy and me on how to get forward with that. Richard wrote a proof of concept for on screen print simulation in GTK. Chris talked a lot about osX printing and did some testing there. His experience on other platforms than Linux helped us a lot to figure out, which path we want to go and way the make sense. I searched for some PDF’s showing the features we need. They can now be found on ColourWiki. Jaroslav Reznik printed them and Till tested them. Michael Vrhel from the Ghostscript project fixed already after the event all of the bugs, which Till worked on in Brno. We had the idea, that some PDF printers might be able to do the right thing with the OutputIntent themselves. While discussing on how to know about that capability, Till and Richard had a nice idea how to reduce code duplication inside the current set of Linux CUPS filters. In parts the Color Management Hackfest crossed over into a Printing Summit.

Jan Grulich started coding on KolorManager. He implemented a widget to show a 2D graph of a ICC profile inside the information tab. Sirko Kemter was not very happy about the colours inside the graph. So I adjusted them, but after the hackfest.

While working on that, Jan profiled his monitor using Dantii’s colord-kde. Yes, Lukáš Tinkl fixed it, so it can now create ICC profiles. We needed to hand massage the profile to get it into Taxi DB, and then thought, it would be good to download the fresh profile later through Oyranos. That worked fine on the command line. But inside KolorManager a selection that a profile is available for download from Taxi DB would be more appealing. Jan wanted to look into that, and I worked later on a API and code snippet for Oyranos.

By the way, the above screen shot is done using the new colour correction feature for KDE-4.10. You might see the strong colour cast in it. Dan Vrátil worked on undoing that cast inside KSnapshot using the actual monitor profile. The initial coding was fast. But he likes to get that working for multiple outputs too.

Casian Andrei, who did the KWin Color Correction project during this years GSoC, wrote some documentation about that newly added feature. While writing that and clarifying some points, we discussed the opt-out inside KWin and found that it is not yet present. Sig. But Casian had played with the idea already and said that per region opt-out would be trivial inside KWin and started to write on that feature during Sunday. In case that works out, it would be trivial to opt out inside existing applications. But we found as well, that for a perfect results only a blending in the correct colour space is needed during compositing. That can be implemented inside toolkits, which is not trivial, and can then be used together with the per window opt-out. That buys us some valuable time for the toolkits to become ready for full colour management support. Whether the same per region approach is easy enough to implement in Wayland needs to be seen.

Now back to profile distribution. Oyranos obtained a new backup tool for Taxi DB. And we counted already over 200 different ICC profiles in the online data base. Sirko Kemter and Daniel Jahre grabbed the taxi sources, installed MongoDB and worked on mostly basic stuff to add later more features. The online front end to the DB can be used on every platform for download and upload. Daniel and Sirko discussed how to temporarily store a ICC profile from the ColorHug LiveCD. We found that the data base can be used for very different things, e.g. distribution of spectral data sets for camera sensors.

Pippin worked since some time on improving the display of gradients on 8-bit driven monitors. He came up with a dithering approach and tested that using the Taxi DB profiles for the analysis of his implementation. That helped him to make the algorithm more robust even with strongly distorted monitor gamma curves. There is quite some interest inside the graphics designers community for his work to solve banding problems. We talked a bit about gegl and I found babl especially interesting. The small library does, what I call pixel layout conversions. Those are in part colour space conversions and encoding conversions. For better separating encoding, 8-bit versus 16-bit etc., from colour spaces, e.g. linear gamma + Rec709 primaries versus sRGB etc., we need better ICC profile analysis. Especially gamma analysis can be improved inside rendering pipelines. Beside discussing hardware stuff, spectral imaging, video processing and so on, he gave a small and very helpful introduction into colour theory, which was a eye opener for many of the colour management newcomers and thus very welcome.

We had a interesting discussion about financial implications of colour measurement hardware. My impression is the high costs and thus reduced availability for good colour measurement gear nags on the success and acceptance of ICC colour management in consumer and professional markets.

During the hackfest it was really a pleasure to have so many experts in the field in one room and work together in a highly productive atmosphere. Some of them I met the first time. So let me thank our sponsors Google, Red Hat and KDE for their generous support of the hackfest idea.

We all worked quite a lot and found such a event should not stay single. So we agreed already to arrange a one day track and one following day at LGM in Madrid / Spain 2013 under the OpenICC umbrella. I hope we will see then even more projects coming.

Yesterday we heard about the arrest of one of our attendees during his journey to the Linux Color Management Hackfest. We where astonished to hear that the Argentinian police issued a international arrest warrant. As Germany is bound by international agreements to follow that, Dantii was arrested in Munich, where he where on transit. In the process of the german justice act his case will be decided. German courts have a notoriously high workload. So it can easily happen that his case might be handled within the next 6 months, which is quite long. The only chance he has is to obtain documents, which can exonerate his person in this case. Therefor his wife tries to come to Munich and bring the needed documents to Germany. Please consider helping Dantii.

The hackfest in Brno is approaching fast. I wrote earlier this year about the idea. It will happen from 9th until 12th November 2012 inside the Red Hat Czech office. Talks with our local organiser and various sponsors went good so far. People will code in Brno on various topics around color management in Linux.

The main focus looks like to be at applications, desktop and library integration. For the printing system and Taxi DB was good interest too. As the event is organised as a framework for attendees, each one will decide, what is best to do. After a morning meeting, where we can coordinate, we will likely split in smaller groups according to a choosen topic or move around as needed. We hope that works for all attendees. There are specialists present for many Linux color topics for discussion and of course color management newbies can ask them to effectively improve their project.

Sirko brought up the idea to organise a hackfest together with developers of applications for Linux desktops and experts interested in colour management. The idea behind that event was to bring interested developers together, support them in implementing color management in their software and move forward that topic across desktops and distributions.

During the recent LGM we found a chance to involve Richard Hughes and planed together about what we like to do during the hackfest. We spotted three main areas of interest: desktop applications including window managers, web browsers and printing. These topics are already worked on, but in a scattered way.

As example, Gwenview is a really great application for managing pictures. But it has no color management implemented yet. Color management in KWin is worked on during the GSoC this year, but in the opposite color management in the compositing manager mutter on the GNOME side is far away as can be read here. Not many web browsers support color management and if they who do, it is often incomplete. The SVG v2 standard will for example introduce additional color management features compared to SVG v1. So it is now the right time to get these implemented in order to be well prepared. For the KDE printing stack there is also a GSoC project this year, but also the Linux Foundation has a working group for this topic.

So, by meeting in person in one place, we want to get something done and build a good understanding of the role of each participating group for a working end to end colour management.

The hackfest will very likely happen in Brno in the Czech Republic at the Red Hat offices. A good time appears later this year 16th till 19th November. Now we like to collect more ideas, speak to people and sort financial issues.